Progress in dendroclimatic studies of mountain pine in northern Thailand

New data added to the existing tree-ring width chronologies of mountain pine (Pinus kesiya and Pinus merkusii) result in a total of seven chronologies for these species for Thailand. The oldest (1647-1993) is from a P. merkusii site at Phu Kradung, north central Thailand. An analysis of the three longest P. kesiya chronologies, from north central Thailand, with Phetchabun rainfall (1951-1992) reveals correspondence between years of low growth and below average rainfall (drought) during the wet season (July-November). The lowest growth year averaged over these three sites during the period of rainfall data (1951-1992) occurred in 1979, coinciding with the lowest wet season rainfall on record. For the common period of tree-ring record prior to 1951 (1830-1950), the level of drought severity in 1979 appears to have been exceeded only twice previously in 1832 and 1894. A P. merkusii record from Thung Salaeng Luang is most significantly correlated with temperatures during May-June, considered a critical period for the subsequent evolution of the Asian monsoon.